Modular ceiling framework

ABSTRACT

A modular framework for a drop ceiling constructed from sheet steel strips in which individual frame members are rolled from a single strip into a cross-sectional shape including a hollow rectangular bulb portion, a flat web portion formed from two thicknesses of the sheet metal strip extending from the center of one wall of the rectangular portion, and a pair of L-shaped portions having one leg of each L-shaped portion lying in a common plane transverse to the web portion and joined respectively to the two thicknesses of the web portion, with the other leg of each L-shaped portion extending parallel to the web and projecting away from the bulb portion. Ends of the web portion have tabs which stab into openings of the web portion of another frame member to form a T connection between cross-members.

FIELD OF THE INVENTION

This invention relates to structural members for constructing theframework of a modular drop ceiling.

BACKGROUND OF THE INVENTION

The use of drop ceilings in building construction is well known. Onemode of construction for drop ceilings is to provide a metal frameworkwith longitudinal runners and lateral cross-members which fit togetherin a lattice network. Standard openings have modular sizes of 2' × 2'squares or 2' × 4' rectangles. The modular framework is supported onhangers from the overhead structure and the framework is used to supportacoustical tile panels, fluorescent light fixtures, ventilationfixtures, and the like.

In the past, both steel grid systems and extruded aluminum grid systemshave been available. The steel grid systems have been constructed fromlengths of T-shaped members which are roll-formed out of sheet steelstock. LSince the acoustical panels rest on top of the inverted T framemembers, the bottom surface of the T is offset from the surface of theacoustical panels. This is not particularly desirable where movablepartition type walls are used, since a gap is formed between the top ofthe partition and the surface of the acoustical panel to allow for thethickness of the inverted T-shaped member. Moreover the flat surface ofthe cross portion of the T that is exposed is relatively wide to achievestiffness and because of its width does not make a particularly pleasingappearance in outlining the grid structure of the drop ceiling.

Drop ceiling frameworks have also been provided which are made fromextruded aluminum. Interlocking of aluminum frame joints presents asomewhat different problem in that either separate clips must beprovided for connecting the parts or interlocking integral tabs providedthat must be bent to lock the parts together. Aluminum extrusions havethe additional disadvantages in that they are not fire resistive andcannot be fire rated. Also, if contrasting tones are desired, thealuminum must be painted after fabrication, by masking techniques,greatly adding to the cost. Thermal expansion is a problem in largefloor plans.

SUMMARY OF THE INVENTION

The present invention provides an improved structure for a drop ceilinggrid or framework in which the structural members are rolled from sheetsteel strips that are pre-punched to provide desired end shapes andholes. A structure is achieved which overcomes the above problems withboth the steel T-shaped frames and the extruded aluminum type ceilingstructures, while retaining the best features of both. The ends of thecross-members are formed with integral clips which allow them to snaponto the longitudinal runners and lock in place in a manner whichprevents any twisting or rotation of the cross-members while eliminatingthe need for any separate clips, brackets, or the like. This isaccomplished, in brief, by providing a frame member comprising anelongated sheet steel strip rolled into a cross-sectional shapeincluding a hollow rectangular bulb portion, a web portion formed fromtwo thicknesses of the sheet metal strip projecting from the center ofone wall of the rectangular bulb portion, and a pair of L-shapedportions having one leg of each L-shaped portion lying in a common planetransverse to the web portion and joined respectively to the twothicknesses of the web portion, the other leg of each L-shaped portionextending parallel to the web and projecting away from the rectangularportion, the edges of the L-shaped portions being turned inwardly towardeach other. The strip can be prepainted with contrasting colors on thetwo sides of the strip before it is rolled into the desired structuralshape. Also, the strip can be pre-punched or cut to provide thenecessary holes and end shapes for connecting the members into a gridand to provide the desired modular spacing or length. One end of thecross-members is formed with the two thicknesses of the web projectinglongitudinally beyond the rectangular portion and the L-shaped portionsto form a projecting connector tab, the tab extending parallel to butoffset from the longitudinal major surfaces of the web. The tab portionhas a cantilevered integrally formed spring clip which locks the tab inplace when it is inserted through a hole in an adjoining longitudinalmember.

DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention reference should bemade to the accompanying drawings, wherein:

FIG. 1 is a perspective view of the drop ceiling framework incorporatingthe features of the present invention;

FIG. 2 is an end view of one of the frame members;

FIG. 3 is a side view of a longitudinal runner;

FIG. 4 is a side view of a cross-member showing the tab connectors atthe end;

FIG. 5 is an assembly side view, partly in section, of cross-memberswith each other and with a runner;

FIG. 6 is an assembly bottom view, partly in section, of intersectingmembers;

FIG. 7 is a perspective view showing the manner in which cross-memberslock in at the ends to a longitudinal runner; and

FIG. 8 is a detail view of the end clip for joining abutting runners.

DETAILED DESCRIPTION

Referring to the drawings in detail, the numeral 10 indicates generallyan assembled framework forming the grid of a drop ceiling. The grid,when assembled, is supported from the overhead structure of the buildingby hanger wires 12. The hanger wires are attached at intervals alongmain longitudinal runners, two of which are indicated at 14 and 16. Themain runners are prefabricated typically in lengths of 12' and normallyare spaced on 4' centers. The runners 14 and 16 are joined bycross-members, as indicated at 18, 20 and 22, which are prefabricated in4' lengths and are joined at their ends to the longitudinal runners 14and 16 in a manner hereinafter described. Typically the cross-members18, 20, and 22 are spaced at 2' intervals, making a grid work of 2' × 4'openings. If desired, additional short members 24 and 26 may be insertedbetween the cross-members 18 and 20 and between the cross-members 20 and22 to form 2' × 2' square modules.

Referring to FIG. 2, the structural members of the framework are formedout of strips of sheet steel by rolling each strip into thecross-sectional shape as shown. By way of example only, the sheet metalstrip may be 0.024 inches in thickness. The center portion of the stripis rolled into a hollow rectangular shape to form a bulb portion 30which is rectangular in cross section with the longitudinal centerlineof the sheet metal strip corresponding to the center of the top surface32 of the bulb portion 30. Integrally joined to the bottom 33 of therectangular bulb portion 30 is a web portion 34 formed by folding thetwo halves of the sheet metal strip at the center of the bottom surface33 of the bulb portion 30 against each other to form a web 34 of doublethickness of the sheet metal strip.

The lower margin of the web portion 34 terminates in a pair of L-shapedportions 36 and 38. The upper leg 40 of the L-shaped portion 36 isintegral with the lower edge of the web portion. The other leg portion42 of the L-shaped portion 36 extends downwardly parallel to the webportion 34. The lower edge of the L-shaped portion 36 is rolled inwardlyto form a lip 44 and is then folded back on itself, as indicated at 46,to provide additional rigidity and to provide a smooth, rounded inneredge 48.

The L-shaped portion 38 is similarly provided with the leg 50 lying in acommon transverse plane with the leg 40 of the L-shaped portion 36. Theother leg 52 extends downwardly and terminates in a lip 54 which isfolded back on itself at 56 to form a smooth inner edge 57. The legs 40and 50 of the L-shaped portions 36 and 38 provide ledges on which aresupported acoustical tiles, for example, such as indicated at 60. Oneedge of the acoustical tile is indented to form a supporting surface 62while permitting the bottom surface 64 to be flush with the inwardlyturned lips 44 and 54 of the frame member.

The frame members are roll-formed into the shape described above inconnection with FIG. 2 by standard roll-forming techniques. By preparingor coating the surfaces of the sheet metal strip with contrasting colorsafter rolling, the interior surfaces of the L-shaped portions form acontrasting color to the reveal provided by the outer surfaces of theinwardly projecting lips 44 and 54, thus giving a pleasing visualeffect.

Referring to FIG. 3, a main runner section is shown which typically is12' in length. The web portion 34 is provided with rectangularpre-punched openings 70 which preferably are spaced at 2' intervals and1' from either end of the runner. The ends of the runner are providedwith separate clips 72 that are riveted or spot welded in place. Asshown in FIG. 8, the clips include a stab portion 74 which is insertedinto an opening 75 in a mating clip of an abutting main runner section.The opening is formed by offsetting a portion of the sheet metal clip,as indicated at 76. A catch 78 near the end of the stab portion 74 actsto lock the clip in place when it is inserted in the opening 75 of thecorresponding clip on the abutting main runner section. The offsetportion extends through the opening in the web of the associated runnerto receive a clip on the opposite side of the web.

The cross-runner members and the manner in which they are assembled intoa grid framework is shown in FIGS. 4- 7. The cross-members, which may bein either 2' or 4' lengths, have integral preformed connector tabs 80 oneach end. The 4' cross-members also have a rectangular opening 82 in theweb at the center.

The manner in which the ends of the cross-members lock into the mainrunners is shown in FIGS. 5, 6, and 7. The tab 80 which is integral withthe web 34 is offset at 84 by an amount equal to the thickness of theweb, i.e., twice the thickness of the sheet steel strip from which thestructural members are formed. The rectangular openings 70 and 82, whichreceive the tabs 80, have a width equal to three times the thickness ofthe web. Thus when the tabs 80 of two cross-members are inserted intothe opening 70 from either side of the main runner, the tabs 80 hold thewebs of the cross-members in alignment in the same plane, as shown inFIG. 6. The tabs 80 are locked in place by integral fingers 86 which areoffset from the tabs 80. The fingers have sufficient spring so that theends snap outwardly after passing through the opening 70 and thusprevent the tabs from being withdrawn after they are inserted.

When assembled, the hollow rectangular bulb portion 30 of thecross-members 20 and 20' terminates in abutting relation to the sides ofthe bulb portion of the main runner 14. The legs 42 and 52 of theL-shaped portions 36 and 38 of the cross-members terminate in abuttingrelation to the outside surface of the corresponding leg 42 on one sideof the main runner and in abutting relation to the outside surface ofleg 52 on the opposite side of the main runner. A notch 90 is formed inthe legs 42 and 52 of the main runner just below the opening 70. Thewidth of the notch is the same as the distance between the insidesurfaces of the legs 42 and 52. The corners of the notch 90 are relievedat 91 to permit extensions of the lips 44 and 54 of the cross-members toextend to the inner margins of the lips of the runner. The inwardlydirected lips 44 and 54 of the cross-members extend beyond the notchededges 92 of the associated legs so as to terminate in alignment with theinner edge 48 of the lip 44 of the main runner when in assembledposition. Thus when completely assembled, a tight interlockingconnection is formed which prevents twisting or rotation of thecross-members relative to the main runners.

What is claimed is:
 1. A drop ceiling comprising a plurality oflongitudinal frame members, each member being formed from a single flatsheet metal strip, each member being formed in cross-section with arectangular shaped hollow tubular portion, a flat web portion in theform of two thicknesses of sheet metal strip projecting from the centerof one side of the tubular portion, and a pair of L-shaped portions eachhaving one horizontal leg extending outwardly from a side of said flatweb portion opposite from the other horizontal leg, and a vertical legextending parallel to but in the opposite direction from said flat webportion to form a channel-shaped portion, the outer margins of thechannel-shaped portion having folded lips projecting inwardly towardeach other, the lateral extent of the outwardly extending horizontallegs being substantially greater than the lateral width of the tubularportion, and means for joining the frame members in a rectangular opennetwork, the intersections of the frame members being formed byconnecting the ends of two frame members to opposite sides of a thirdmember to form a pair of T-joints at spaced intervals along the thirdmember, the third member having the parallel vertical legs andassociated folded lips of the two L-portions notched at eachintersection with the adjoining two members, each of the adjoiningmembers at an intersection having the folded lips projecting beyond theends of the associated L-shaped portions so as to fit between thenotched edges of the adjoining folded lips of the third member with theends of the associated L-shaped portions abutting edgewise against thesides of the parallel vertical legs of the third member at the marginsof the notches in the parallel vertical legs of the third member, eachof the two frame members being terminated in a connector tab formedextending and offsetting a portion of the two thicknesses of the weblongitudinally beyond the rectangular portion and the L-shaped portions,the tab extending parallel to but offset from the longitudinal majorsurfaces of the associated flat web portion, the connector tabs of saidtwo frame members extending through an opening in the flat web portionof the third member from opposite sides in overlapping relationship, thetabs having intergral fingers projecting from the tab and engaging theflat web portion adjacent the opening to lock the members together, andpanels supported in the rectangular openings of the framework themargins of the panels being notched to receive the L-shaped portions sothat the panels are supported on the outwardly projecting horizontallegs of the L-shaped portions and the outer surface of the panels isflush with the folded lips.
 2. The apparatus of claim 1 wherein theinwardly turned edges of each frame member are doubled over to doublethe thickness and form a rounded inner margin.
 3. The apparatus of claim1 wherein the sheet metal strip is coated before being rolled in shapewith a layer of material providing contrasting shades of color onopposite surfaces of the strip.